The invention is useful in the field of health care, where reliable analysis of samples for components contained therein is needed. Chemical reactions needing heating are well known, for example from molecular diagnostics, where nucleic acids are known to denature, i.e., to become single stranded from a hybrid of two strands, by applying heat above the melting temperature of the hybrid.
A method that uses reactions cycles including such denaturation step is the polymerase chain reaction (PCR). This technology has revolutionized the field of nucleic acid treatment, particularly the analysis of nucleic acids, by providing a tool to increase the amount of nucleic acids of a particular sequence from negligible to detectable amounts. PCR is described in EP 0 201 184 and EP 0 200 362.
An instrument for performing thermocycles in controlled manner on samples in tubes using heating and cooling an extended metal block is disclosed in EP 236069.
Heating of PCR mixtures is presently mainly done using Peltier elements with active heating and cooling. Those require complex electronics compared to systems with active heating and passive cooling.
In U.S. Pat. No. 6,633,785 there is described a method for heating a micro-tube using either resistance heating or inductive heating.
In U.S. Pat. No. 6,602,473 there is disclosed a microfabricated reaction chamber made from silicon. The device has inlet and outlet ports and can be used to conduct PCR reactions when inserted into an instrument. The system does, however, not allow sensitive and quick temperature control.
In WO 98/39487 there is described an apparatus for holding a device having a chamber, said apparatus comprising heating or cooling plates arranged on opposite side walls of a flat device in case the device is inserted into said apparatus.
The temperature changes provided by the prior art instruments were relatively slow. Thus, there was a need to provide faster temperature changes in fluids, particularly during amplification of nucleic acids.